As above, good for loosening and removing soil from nooks and crannys on coins/jewellery, but anything harder than that and they aren't so effective.

If you want to clean bulk lots of coins, especially beach coins with corrosion, a rock/gemstone tumbler is the way to go, though might seem too expensive for some. They can be purchased from most lapidary shops, Lortone is probably one of the more well known brands out there.

I have seen home made tumblers made from copy machines. BUT here is a Xpo of above product you be the judge. B4. I have used the key way to represent a flat coin & a 1921 penny (seen better days). 15 min wipe - turn (change water)15 min. ..My thoughts , not a coin restorer device. Maybe more affective on jewellery It worked on the ring I found recently.